Microgravity Science and Technology最新文献

The phenomenon of solidified suspended hollow droplets is often run into industry and nature. In this study, we focus on the containerless solidification process of a hollow droplet undergoing a forcing flow. We found that when the radius ratio (R_io) varied with different growth angles, it changes the trend of the solidification rate of the solidifying front over time. Specifically, with the growth angle of 5° (i.e., Φ_gr = 5°), the suspended hollow droplets finished solidification in almost the same time for R_io in the range of 0.2–0.7. When we increase the growth angle by 5°, i.e., Φ_gr = 10°, the solidification time increases with the increase of R_io. Also following the increase of R_io, this increase in the solidification time is even higher for the growth angle Φ_gr = 15°. The inlet temperature is also considered. Obviously, increasing the inlet temperature increases the solidification time of the hollow droplets. In addition, when the Reynolds number increases, the solidification time of the droplets also tends to increase. However, the increment of this trend is different under different temperatures of the forcing flow.

The examination of the impact of microgravity on biological systems has gained considerable attention owing to its potential implications for health and disease. Simulated microgravity serves as a valuable methodology for elucidating the intricate cellular responses to altered gravitational conditions. This study investigates the effects of simulated microgravity on cellular DNA, employing four distinct cell lines—breast, brain, and esophageal cancer cells, in conjunction with normal cells for comparative analysis. The experiment utilized the comet assay test to quantitatively assess DNA damage. The results revealed a discernible disparity in the response to simulated microgravity, notably with cancer cells exhibiting a significant increase in DNA damage compared to the relatively minimal effects observed in both control and normal cells. Furthermore, within the cancer cell lines, significant variations in the extent of DNA damage were evident, implying a cell type-dependent response to simulated microgravity. These findings illuminate the potential differential susceptibility of cancerous and normal cells to microgravity-induced DNA damage. Consequently, this research substantially contributes to our comprehension of microgravity-induced cellular responses and unveils promising avenues for targeted interventions in cancer therapy.

This paper delves into the dynamics of surface-active bubbles under low-frequency acoustic waves, with a focus on the stability effect and basic principle of rupture. The Rayleigh-Plesset equation is extended and modified based on real biological data, resulting in a model of surface-active bubbles with nonlinear surface tension. Using the Runge-Kutta method for numerical calculations, it is observed that larger acoustic wave amplitudes lead to larger bubble amplitudes. The acoustic wave frequency only affects the bubble vibration frequency in the low-frequency range, but at the resonance frequency, the bubble oscillations are violent. To further explain bubble rupture, the stress-strain relationship of the surface active layer of the bubble is studied, with the stress on the wall increasing sharply with the bubble radius. The stability of the non-spherical interface of the surface-active bubbles reveals a critical radius value, with bubbles in a stable state when the radius is smaller than this value. Through simulation, it is observed that bubbles vibrate in a steady state under stable conditions, but when the radius exceeds the critical value, a non-spherical interface appears ultimately resulting in inward depression and rupture.

Repeated jumping has been demonstrated as a feasible exercise countermeasure in microgravity and has been shown to reduce deconditioning in head down bed rest studies. However, varying landing stiffness may provide greater contribution of both axial and medio-lateral bone strain and muscle loading at greater muscle lengths, which may help minimize bone and muscle deconditioning. Therefore, this study investigated the effect of different landing styles on the force profile and ground contact time during repeated jumping using HIFIm in microgravity. Two participants performed repeated jumping on the HIFIm jump sled in microgravity during a parabolic flight campaign. ‘Ground’ forces and ground contact time were compared between landing styles where increased landing stiffness was instructed to the jumper, and increased spring resistance. The results show that the forces experienced when performing repeated jumps in microgravity are sensitive to the landing style employed. As greater stiffness was instructed, peak forces increased, and ground contact time decreased significantly. Peak forces and ground contact time also significantly increased when spring resistance increased. These results highlight that landing instructions and spring configurations could be used as training variables when developing an astronaut training program, which can use different jump styles to minimize bone and muscle deconditioning. Further research using bed rest analogs and repeated jumping using HIFIm is needed to demonstrate varied repeated jumping interventions as an effective exercise method for minimizing deconditioning in astronauts.

The launch is considered the most stressful rocket flight stage due to the hypergravity occurrences. The possibility of using honey bees (Apis mellifera) as the extraterrestrial pollinator depends on their ability to reproduce correctly after experiencing hypergravity. The described study aims to verify the impact of a launching rocket’s acceleration on honey bee queen’s egg-laying behavior. Four artificially inseminated A. mellifera carnica queens were placed in the Human Training Centrifuge and given to the acceleration pattern of the launching Soyuz rocket. Next, the data on the number of food stores, eggs, larvae, and worker and drone pupae were collected from the test and control hives using the modified Liebefeld method. The pilot study results imply that accelerated queen’s egg-laying behavior may change twofold: limiting or maximizing the number of laid eggs, with the control queen egg-laying rate remaining stable for all samples. The number of drone pupae is greater for the test sample colonies, with its earlier appearance in the hive. No impact on overwintering success was observed. Authors indicate limitations of the results and a need to continue the study to verify the occurrence of anomalies potentially related to the examined factor.

Lithium-ion batteries are a feasible solution to store energy efficiently. However, in safety-critical environments such as the suborbital rockets, the introduced technologies do not may compromise safety. This research explores the possibility of replacing Ni-MH batteries with Li-ion batteries. However, before replacing technologies, the reliability of Li-ion cells needs to be evaluated, and the potential benefits must be considered against the risks to ensure the mission’s success. The main objective is to ensure the safety and integrity of suborbital missions during the technology transition. To assess the technology exchange, a method where the battery cell experiences a sequence of tests that cover aspects of safety encountered during the vehicle missions, such as vacuum, capacity, short circuit behavior, over-current discharge, behavior at higher environment temperature, and pulsed discharge behavior. To experience the proposed method, two Li-ion cells commercial off-the-shelf (COTS) from different manufacturers are evaluated. The results indicated that only one of the two cell models evaluated can substitute the Ni-MH. This research concludes that replacing Ni-MH cells with Li-ion cells is feasible, for such an application. The proposed acceptance flow design based on the test collectively validates the replacement, showing that the Li-ion cells can offer reliability, safety, and efficiency to suborbital vehicles to fulfill this mission profile.

Microgravity offers an enticing synthetic knob for materials scientists to explore—however, this environment creates major challenges in hardware development that can turn a simple 3-day experiment into a 3-year long nightmare. This paper provides an overview of engineering an autoclave, compatible with NASA’s Solidification Using a Baffle in Sealed Ampoules (SUBSA) furnace, to enable microgravity hydrothermal synthesis—an acceleration-sensitive technique that processes aqueous samples above the boiling point of water. Hydrothermal synthesis is a universal chemical transformation technique that is used to produce a range of advanced materials with applications in alternative energy, healthcare, and the food industry. In this work, we use the synthesis of graphene hydrogel as a case study to verify our hardware design on Earth before launching to the International Space Station for microgravity testing. The design addresses pertinent challenges which include enabling thermal expansion while preventing air bubble formation in solution and implementing a pressure fail-safe above the maximum operating temperature. Our goal in presenting this autoclave design is to provide a step forward towards commercial-of-the-shelf microgravity hardware.

This paper numerically analyzes the influence of Dufour/Soret and space-dependent internal heat source (exponential decaying form) on combined convection (entire regime) of non-Newtonian fluids (power-law model of Ostwald-de-Waele) flow past a vertical full cone in porous media with the boundary conditions of VHF/VMF case. The transformed governing equations (non-similar equations) are solved by Keller box method (KBM). Numerical data for the dimensionless temperature profile, the dimensionless concentration profile, the local Nusselt number and the local Sherwood number are graphically and tabularly presented for the nine parameters: the buoyancy ratio (N), the Lewis number (Le), the Dufour parameter (Df), the Soret parameter (Sr), the cone angle parameter (m), the mixed convection parameter (xi), the VHF/VMF exponent (lambda), the non-Newtonian fluid power-law index (n), the space-dependent internal heat source coefficient ({A}^{*}). The increase of the buoyancy ratio (N) and the VHF/VMF exponent (lambda) tends to increase both the local Nusselt number and the local Sherwood number. The Nusselt number enhances with increasing the Soret parameter (Sr). Increasing the Lewis number (Le), the Dufour parameter (Df), the space-dependent internal heat source coefficient ({A}^{*}) enhances the Sherwood number. When the power-law index (n) is decreased, the local Nusselt and Sherwood numbers are increased. The physical aspects of the problem are discussed in details.

A numerical modelling of electrophoresis of dielectric particle is proposed under low and moderate homogeneous electric fields. As surface charge at the surface of the particle increases, nonlinear effects associated with surface conduction become more prominent. Current analytical methodologies addressing this issue employ asymptotic techniques, necessitating the establishment of effective boundary conditions. Consequently, solutions within the thin boundary layer, which substantially contribute to the emergence of nonlinear phenomena, are overlooked. While the asymptotic approach is capable of capturing principal effects, it falls short in providing a comprehensive understanding of the complete picture with non-linear effects. Our numerical modelling, incorporating a full formulation, is designed to bridge this knowledge gap. The numerical algorithm is tested in this work for the case of dielectric particle and can be readily extended to other particle types by altering the boundary conditions. The proposed method can be effortlessly generalized for various particle categories, such as ion-selective, flexible, biological, Janus particles, and those with hydrophobic surfaces. It operates without constraints concerning Debye, Dukhin, and Péclet numbers, which are associated with the emergence of nonlinear effects. The numerical algorithm was validated using an analytical solution for a weak electric field and experimental results for moderate and high electric fields. It was found that the electric field intensity and the surface charge density on the particle have the most significant impact on the emergence of non-linear effects. When there is a high degree of non-linearity, a structure of thin boundary layers nested within one another forms around the particle’s surface. In particular, the formation of a space charge region (SCR) around a non-conducting surface was discovered. It was previously believed that SCR only forms around surfaces with ion-exchange properties.

Opposed-flow flame spread over solid materials has been investigated in the past few decades owing to its importance in fundamental understanding of fires. These studies provided insights on the behavior of opposed-flow flames in different environmental conditions (e.g., flow speed, oxygen concentration). However, the effect of confinement on opposed-flow flames remains under-explored. It is known that confinement plays a critical role in concurrent-flow flame spread in normal and microgravity conditions. Hence, for a complete understanding it becomes important to understand the effects of confinement for opposed-flow flames. In this study, microgravity experiments are conducted aboard the International Space Station (ISS) to investigate opposed-flow flame spread in different confined conditions. Two materials, cotton-fiberglass blended textile fabric (SIBAL) and 1 mm thick polymethyl methacrylate (PMMA) slab are burned between a pair of parallel flow baffles in a small flow duct. By varying the sample-baffle distance, various levels of confinement are achieved (H = 1–2 cm). Three types of baffles, transparent, black, and reflective, are used to create different radiative boundary conditions. The purely forced flow speed is also varied (between 2.6 and 10.5 cm/s) to investigate its interplay with the confinement level. For both sample materials, it is observed that the flame spread rate decreases when the confinement level increases (i.e., when H decreases). In addition, flame spread rate is shown to have a positive correlation with flow speed, up to an optimal value. The results also indicate that the optimal flow speed for flame spread can decrease in highly confined conditions. Surface radiation on the confinement boundary is shown to play a key role. For SIBAL fabric, stronger flames are observed when using black baffles compared to transparent. For PMMA, reflective baffles yield stronger flames compared to black baffles. When comparing the results to the concurrent-flow case, it is also noticed that opposed-flow flames spread slower and blow off at larger flow speeds but are not as sensitive to the flow speed. This work provides unique long-duration microgravity experimental data that can inform the design of future opposed-flow experiments in microgravity and the development of theory and numerical models.